1. Technical Field
Embodiments of the present invention relate to a liquid ejecting head that ejects liquid by driving piezoelectric elements and a liquid ejecting apparatus including the piezoelectric elements. More particularly, embodiments of the invention relate to a liquid ejecting head capable of preventing configuration members from being damaged due to stress generated when the piezoelectric elements are driven, and to a liquid ejecting apparatus.
2. Related Art
A liquid ejecting apparatus is an apparatus that includes a liquid ejecting head and that ejects various types of liquid from the liquid ejecting head. Image recording apparatuses such as ink jet type printers or ink jet type plotters are examples of liquid ejected apparatuses. In recent years, a liquid ejecting apparatus is used in various types of manufacturing apparatuses because the liquid ejecting apparatus can accurately place an extremely small amount of liquid in a predetermined position. For example, a liquid ejecting apparatus is used in a display manufacturing apparatus that is used to manufacture color filters of a liquid crystal display or the like, in an electrode forming apparatus that is used to form electrodes of an organic Electro Luminescence (EL) display, a Field Emission Display (FED), or the like, and in a chip manufacturing apparatus that is used to a manufacture biochip. Further, liquefied ink is ejected from a recording head for the image recording apparatus, and solutions of respective color materials, that are, R (Red), G (Green), and B (Blue) are ejected from a color material ejecting head for the display manufacturing apparatus. In addition, liquefied electrode material is ejected from an electrode material ejecting head for the electrode forming apparatus, and a bio organic substance solution is ejected from a bio organic substance ejecting head for the chip manufacturing apparatus.
The liquid ejecting head is configured to introduce liquid into pressure chambers, generate a change in pressure of the liquid in the pressure chambers, and eject the liquid from nozzles that communicate with the pressure chambers. The pressure chambers are formed in a silicon crystalline substrate (hereinafter, referred to as a pressure chamber forming substrate) by anisotropic etching with excellent dimensional accuracy. In addition, piezoelectric elements are used as a pressure generation section. The pressure generation section generates change in the pressure of the liquid in the pressure chambers.
There are various configurations of such a piezoelectric element. For example, a piezoelectric element may be configured in such a way that a lower electrode is located on a close side to the pressure chamber. A piezoelectric layer that is formed of a piezoelectric material, such as lead zirconate titanate (PZT), and an upper electrode are respectively laminated and patterned on the lower electrode using a film formation technology. Further, one of the upper and lower electrodes functions as an individual electrode that is provided for each pressure chamber, and a remaining one of the upper and lower electrodes functions as a common electrode that is common to a plurality of pressure chambers. With regard to the piezoelectric film, a portion of the piezoelectric film that is interposed between the upper and lower electrodes is an active portion. The active portion deforms due to the supply of a voltage to the electrodes. A portion that is separated from one or both of the upper and lower electrodes is an inactive portion that does not deform due to the supply of the voltage to the electrodes.
A configuration of the liquid ejecting head is proposed in which a piezoelectric layer is formed in a series in a state in which openings of a plurality of pressure chambers are covered on a pressure chamber forming substrate (for example, refer to JP-A-2003-311954). That is, one piezoelectric layer is provided that is common to the plurality of pressure chambers. A portion of the piezoelectric layer, which is interposed between upper and lower electrodes, functions as an active portion (activated layer). An active portion corresponds to each pressure chamber. In this configuration, when a predetermined active portion is deformed, an unnecessary portion (e.g., an active portion that corresponds to neighboring pressure chambers) is also deformed. Thus, there is a problem in that so-called adjacent crosstalk is generated. In JP-A-2003-311954, grooves, which are formed by partially removing the piezoelectric layer, are provided to surround the peripheries of the openings of the pressure chamber. The grooves can prevent or reduce stress, generated when a predetermined active portion is deformed, from being transferred to adjacent active portions. Thus it is possible to reduce the so-called crosstalk.
However, in the related-art configuration, stress is concentrated on corners of an opening portion of a pressure chamber that has a polygonal shape. More specifically, stress may be generated on sharp corners in accordance with the deformation of the active portion, and thus there is a problem in that damage, such as cracks, may occur in a pressure chamber forming substrate that is configured from a silicon substrate or in a head configuration member, such as a piezoelectric layer.